The present disclosure generally relates to manufacturing methods and apparatuses for producing in a continuous mode, a hot melt adhesive that incorporates an adhesion promoter, such as a stabilized silane compound.
Xerographic digital presses, such as the XEROX IGEN3 press have been developed for the production of publications, such as book-on-demand, brochures and manuals. Many of such applications involve bookbinding by applying a hot melt adhesive. However, poor adhesion may result using conventional adhesives due to fuser oil contamination on the xerographic print.
In a typical imaging device, a light image of an original to be copied is recorded in the form of a latent image upon a photosensitive member, and the latent image is subsequently rendered visible by the application of resin particles and pigment particles, or toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image may be fixed or fused upon a support, which may be a support sheet such as plain paper, using a fuser roll.
To ensure and maintain good release properties of the fuser roll, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, nonfunctional silicone oils or mercapto- or amino-functional silicone oils, to prevent toner offset. However, these fuser oils can significantly lower the surface free energy of the xerographic print, thereby reducing the adhesion of an adhesive used to bind xerographic prints into a book, manual, or the like.
The addition of an adhesion promoter to hot melt adhesives or pressure sensitive adhesives improves adhesion to very low surface free energy substrates. The adhesion promoter improves the thermal stability of the adhesive and the viscosity of the adhesive remains relatively constant at temperatures, for example, ranging from about 100° C. to about 200° C. The adhesive containing the adhesion promoter is thus able to bind very low surface free energy substrates such as Xerographic prints contaminated with fuser oil, and maintains a substantially stable viscosity at adhesive application or operating temperatures from about 100° C. to 200° C.
An example of an adhesion promoter that is well suited for hot melt adhesives used with xerographic prints is a hydrolytic silane compound admixed with aqueous buffer solution. These compounds are described in co-pending U.S. patent application Ser. No. 11/623,509, filed Jan. 16, 2007, the entirety of which is herein incorporated by reference. As described in this disclosure, the hydrolytic silane compound may include at least one silane group of —Si(R)3-mXm, wherein R is a non-hydrolyzable organic group, X is a hydrolytic group and m is an integer of 1 to 3.
Typically, a hot melt adhesive that includes an adhesion promoter is made using a batch process, often due to the small quantities of adhesive needed at one time. A problem that may occur during a batch process is the degradation of the hot melt adhesive if the adhesive is stored for too long at the temperature at which the reaction between the hot melt adhesive and the adhesion promoter occurs. Another problem that may result from batch processing is inconsistency between the end products from different batches. Finally, an adhesive that incorporates a conventional adhesion promoter may encounter issues associated with the pot life of the adhesive. That is, the adhesive may not be able to be kept long enough in a hot pot to meet the requirements during the application process, for example in bookbinding applications. The viscosity of the adhesive containing a conventional adhesion promoter may continuously increase and cause operating problems.
It is thus desirable to avoid these problems by using a manufacturing process and apparatus that allows the hot melt adhesive containing an adhesion promoter to be produced in a continuous mode, thereby maintaining the thermal stability of the adhesive, sufficiently long adhesive pot life and constant viscosity of the adhesive during the application process.